1. FIELD OF THE INVENTION
The invention relates to a method for rolling a metal strip in a rolling mill which has a rolling mill train of one or more roll stands. The invention also relates to a control system for operating the rolling mill in accordance with the method.
2. DESCRIPTION OF THE PRIOR ART
In one known method of rolling metal strip in a rolling mill, before the metal strip enters the rolling mill train, the roll stands are preset in accordance on a predetermined necessary roll force F.sub.i during rolling in the roll stand i, which roll force F.sub.i is determined by the formula F.sub.i =K.sub.i *KSB.sub.i, in which K.sub.i is a multiplication factor and KSB.sub.i is the deformation resistance of the metal strip during rolling through the roll stand i. In this specification * is used as a multiplication sign.
It is customary in this method for allowance to be made in the multiplication factor K.sub.i for a geometrical factor which takes into account the shape of the strip in the roll gap, and also for a factor for the length of the contact arc in the roll gap.
The method is known in the practice of users of installations for hot rolling of steel strip. These users are confronted with a market demand for greater variety in rolled products. This means that the roll stands of the rolling mill train have to be adjusted very often in order to be able to make rolled products of the various required types. Changing the presetting leads to a learning phase during the following rolling process. During the learning phase the adjustment of the various roll stands is optimised.
During the learning phase the quality of the rolled product achieved is however less than satisfactory. Furthermore, quality requirements have become stricter in recent years, which also gives rise to more stringent requirements on the accuracy of the presetting of the roll stands. In the known method, both aspects, greater variety and higher quality requirements, lead to an increase in finished product rejection.